Combined lighting and sound absorbing fixture



COMBINED LIGHTING AND SOUND ABSORBING FIXTURE Filed Dec. 12, 1949 2 Sheets-Sheet l CARL W. LEMMERMAN a 0.0m 0. SMITH, JNVENTORS.

A TTORNEK 6, 1955 c. w. LEMMERMAN ET AL 2,715,449

COMBINED LIGHTING AND SOUND ABSORBING FIXTURE 2 Sheets-Shee 2 Filed Dec.

CARL W. LEM/HERMAN 8 CLOVD 0. SMITH,

INVENTORS.

ATTORNEY.

United States Patent PHI COMBINED LIGHTING AND SOUND ABSORBING FIXTURE Carl W. Lemmerman, Hartford, Conn., and Cloyd D. Smith, Los Angeles, Calif.

Application December 12, 1949, Serial No. 132,522

10 Claims. (Cl. 181-30) This invention relates to sound absorbing units and more particularly to a combined lighting and soundabsorbing fixture, and especially to a sound-absorbing unit which is adapted for attachment to a lighting fixture.

After a building has been completed, it is quite common for its occupant to discover that sound-absorption treatment is required. Furthermore, the application of sound-absorption treatment to a new building at the time of its construction is quite often such a large added expense that such treatment is postponed even when the need for it is known.

For these and other reasons, it is not uncommon for an owner or other occupant of a building, whether it be a dwelling house, an oflice building, or a store, to add sound-absorption treatment to the building after it has been completed and has been in use for some time. The presence of lighting fixtures, especially overhead lighting fixtures such as those commonly installed in stores and oflices, and the presence of other structural features, frequently render the installation of sound-absorbing material on the walls diificult and expensive.

It is therefore the principal object of this invention to provide an improved method of treating a room already containing lighting fixtures with sound-absorb ing material.

Another object of this invention is to provide a combined lighting and sound-absorbing fixture which is readily mounted in a room.

A still further object of this invention is to provide a sound-absorbing unit which may be readily attached to a lighting fixture already mounted in a room.

The foregoing and other objects of the invention will appear more fully upon consideration of various embodiments of the invention which are illustrated in the accompanying drawings and described below.

In the drawings wherein like reference characters indicate like elements throughout the several views:

Figure 1 is a perspective view of a combined lighting and sound-absorbing fixture embodying the features of this invention;

Figure 2 is an end view of the fixture illustrated in Figure 1;

Figure 3 is a perspective view showing a series of such fixtures butted together in a line;

Figure 4 is a perspective view of such fixture having its end capped;

Figure 5 is a perspective fragmentary view of an alter native embodiment of the invention and Figure 5a is a perspective view of a modification thereof;

Figures 6, 7, and 8 are end views of other alternative embodiments of the invention; and

Figure 9 is a detailed fragmentary view of an alternative method of connecting a sound-absorbing unit to a lighting fixture.

Referring to Figures 1 and 2, there is illustrated an embodiment of the invention consisting of a fixture 10 comprising a pair of sound-absorbing units 11 attached to a fluorescent lighting unit 20. The lighting unit which is of conventional construction, comprises an elongated trough 22 which is concave downwardly and which is provided with suitable brackets 24 for supporting elongated fluorescent tubes 26 within the concave, or lower, side thereof. The concave side of the trough 22 is coated with a suitable light reflecting paint or enamel. The lighting fixture 20 is supported from a ceiling (not shown) by means of a pair of chains 28 connected to opposite ends of trough 22. Electrical connections to the lights 26 are made in a conventional manner through opposing contacts (not shown) supported on the brackets 24 and by means of a step-up transformer (not shown) contained in a box 30 supported on the upper, or convex, side of the trough 22, and a cable 32 that leads upwardly to a connector (not shown) in the ceiling. Outwardly extending flanges 34 formed at the lower side edges of the trough 22 are conveniently used for supporting the lower ends of the sound-absorbing units 11.

Each of the sound-absorbing units 11 comprises a perforated sheet 12 of U-shape in cross section. Each of the sheets 12 is provided with a relatively short leg 13 and a relatively long leg 14. The ends of the relatively long legs 14 overlap and the overlapping portions 15 are fastened together by any suitable means such as screws. The two overlapping edges or flanges of the perforated sheets 11 are notched to provide openings 18 through which the chains 28 pass. The ends of the relatively short legs 13 rest upon the flanges 34 and are secured thereto by any suitable means such as screws. Each of the sheets 12 is provided with perforations of a suitable size and number to render the sheets acoustically transparent. The principles of designing such transparent sheets are well-known and need not be described in detail here. One method of achieving such transparency is described, for example, in Patent No. 1,726,500 issued to R. F. Norris on August 27, 1929.

A blanket or sheet 16 of fibrous sound-absorbing material is secured by means of a suitable cement to the inner side of each of the sheets 12 covering the entire interior surfaces thereof except for the overlapping portions 15. Such blankets may be made of mineral Wool, Fiberglas or any other porous material capable of absorbing sound by viscous action. While other types of sound-absorbing material might be employed, fibrous material is ideally suited to the present invention since it has been determined experimentally that a body of fibrous sound-absorbing material has an effective sound absorption area greater than the geometrical or optical cross-section at least for sound waves having a wave length less than about one half the average radius of the body. (See Journal of Acoustical Society of America, volume 17, page 322 (1946) and volume 21, page 169 (1949)). Furthermore, since such fibrous material possesses a very high sound-absorption co-efiicient and the sheets 12 to which they are attached are acoustically transparent substantially all sound impinging upon the sound-absorption units It) is absorbed.

It is to be noted that the combined lighting and soundabsorhing fixture 10 illustrated in Figs. 1 and 2 comprises a tubular sheet structure formed by the trough 22 and the two perforated sheets 11; and that a blanket of fibrous sound-absorbing material is secured in an annular layer to the inner side of the sheet structure over all the portions thereof that are perforated. This sheet structure is of oval or elliptical configuration having a horizontal major axis of about 18 to 24 inches and a vertical minor axis of about 8 to 12 inches. As a result, the fixture possesses a large optical cross-section as viewed vertically, and a relatively small cross-section as viewed horizontally. For this reason, the unit is more effective in absorbing sound that is travelling vertically in a room than sound which is travelling horizontally. This feature is particularly advantageous where the fixtures are mounted near the ceiling and most of the sound to be absorbed is generated near the floor of the room to be treated. Also with this type of mounting, increased effectiveness in absorbing sound is achieved in that sound reflected from the ceiling strikes the upper portion of the unit.

In Fig. 3 there is illustrated an arrangement in which three combined lighting and sound-absorbing fixtures are connected in a line. In this case, the ends of the successive sound-absorbing units and lighting units are butted together and are joined by means of bands 42 which overlap the adjoining ends of adjacent perforated sheets and are secured thereto by any suitable means such 7 as screws. If desired to improve appearances, the outer ends of the outermost fixtures in the line are closed by means of perforated caps 43 secured thereto by means of screws as illustrated in more detail in Fig. 4. For most effective sound-absorption, blankets 44 of soundabsorbing material are cemented to the inner surfaces of these caps 43. However, these blankets 44 may, if desired, be omitted in order to facilitate the convection of air through the interior of the shells to facilitate cooling of the transformer boxes 45. A relatively large volume remains within the tubular structure so that a large volume of air contacts the transformer boxes 45 to facilitate cooling thereof.

In case pipes 46 are employed instead of chains 28 to support the fixtures from a ceiling, the wires that supply electrical power to the lighting fixtures are led upwardly through the pipes in order to improve appearances.

The embodiment of the invention illustrated in Fig. 5 is similar to that illustrated in Figs. 1 and 2 except that the trough 22 is also perforated to render it substantially acoustically transparent and blankets 52 of fibrous sound absorbing material are secured to the upper or convex side of the perforated portions of the trough. This enhances the sound-absorbing efficiency of the combined fixture.

Furthermore, it will be noted that some absorption of sound can be achieved with a lighting fixture of the type illustrated in Fig. 5 even if the sound-absorbing units 11 are not employed. In such a case, as large a portion of the trough as possible is covered with sound-absorbing material and the appearance of the unit is improved by covering the upper portions thereof with acoustically transparent perforated sheets 54 as indicated in Fig. 5a. In the case illustrated, the entire portion of the trough lying between the transformer box 56 and the side edges of the trough are covered with blankets 52 of fibrous sound-absorbing material and the perforated cover sheets 54 are attached at their lower edges to the flanges 58 at the outer edges of the trough and at their upper edges to the side edges of the transformer box 56.

In the embodiment of the invention illustrated in Fig. 6, the trough 22 of the lighting fixture 20 is of the same configuration as that illustrated in Figs. 1, 2 and 5. In this case, however, the sound-absorbing units are of V-shape in cross-section. Each of these units comprises a relatively short leg 72 which is attached to the flange 34 at the respective lower edges of the trough and a relatively long leg 74. The two long legs 74 overlap at the top and are suitably secured together in the manner hereinbefore described.

In the embodiment of the invention illustrated in Fig. 7, a pair of sound-absorbing units are supported upon the upper half of an elliptically-shaped lighting fixture 82. In this case, the lighting fixture 82 is not provided with any outwardly directed flanges. The two sound-absorbing units 80 are of the same general type as those hereinabove described employing a perforated sheet 84 to which are secured blankets 86 of fibrous sound-absorbing material. However, in this case, the cross-sections of the units are in the form of quarter-ellipses. The perforated sheets of which these units are made are connected together in overlapping portions 86 at the top and they are provided with inwardly directed flanges 88 at the bottom. These flanges are interconnected by means of straps 90. The straps 90 rest upon the upper side of the fixture 82 and are of just suflicient length to hold the lower edges of the units 80 close to the sides of the fixture 82.

In the embodiment of the invention illustrated in Fig. 8, the principles of the invention are applied to a lighting fixture which is fastened to a ceiling 102 in direct contact therewith instead of being hung therefrom by means of chains 28 or pipes 46. This lighing fixture comprises an inverted trough 104 having flanges 106 at the side edges threeof. To each of the flanges 106 there is secured a sound-absorbing unit 110 which comprises a perforated sheet 112 having a straight horizontally extending portion directly attached to the corresponding flange 106 and an upwardly curving portion 114 that is provided at its upper end with an inwardly curved hook 116 which is adapted to fit within a bracket 118 in the ceiling. In the event that the inverted trough 104 is provided with an upwardly directed flange 120 at its side edge as shown in Fig. 9 instead of a horizontally directed flange 106 as indicated in Fig. 8, the perforated sheet 112 is provided with a downwardly directed flange 122 which may be attached to the trough flange 120 by means of screws 124. In either event, the sound-absorbing units 110 are positioned on the brackets 118 by sliding them horizontally and parallel to the length of the lighting fixture 100 and then securing their lower ends to the flanges 106.

All of the sound-absorbing units described hereinabove are of cylindrical configuration, that is, their surfaces may be generated by the movement of a generating line along a non-rectilinear line while maintaining the generating line parallel to a fixed line. For this reason by employing such units that comprise flexible blankets of fibrous sound-absorbing material secured to one side of a thin rigid sheet, the flexibility of the sound-absorbing units is enhanced because they may be readily bent to some degree at least without breaking or otherwise injuring the sound-absorbing material. Units of the general configuration described are particularly useful to employ as attachment for fluorescent lighting fixtures of conventional shape, especially since many of such fixtures are provided with cylindrical troughs bearing outwardly extending flanges at their lower side edges. Thus it is seen that a room in which such lighting fixtures have already been installed may be readily treated acoustically by employing such sound-absorbing attachments.

While the invention has been illustrated and described with particular reference to attachments suitable for installation on fluorescent lighting fixtures, it is clear that the principles of the invention are applicable to other types of lighting units as well. Furthermore, it will be obvious that though the invention is primarily directed to the provision of a sound-absorbing unit which may be attached to lighting units that are already in place, actually the invention also provides a combined lighing and sound-absorbing fixture which may be separately sold and which may be installed at the outset when a building is being constructed.

Although only certain embodiments of the invention have been illustrated and described in detail, further changes and modifications in form, material, and relative arrangement of parts, which will now be apparent to those skilled in the art, may be made without departing from the scope of the invention. It is therefore intended to cover all such modifications that fall within the scope of the appended claims.

The invention claimed is:

1. A combined lighting and sound-absorbing fixture comprising: an elongated downwardly concave trough member in said trough for supporting an elongated light source within the concave side thereof, the concave side of said trough being adapted to reflect a substantial portion of light impinging thereon, said trough being perforated to such a degree as to render said trough substantially acoustically transparent but substantially optically opaque, and a body of fibrous sound-absorbing material secured to the convex side of said trough whereby a large proportion of the sound impinging on the lower side of the perforated portion of said trough is absorbed, and common means for hanging said trough and said body of material from a ceiling of a room.

2. A combined lighting and sound-absorbing fixture comprising: a tubular sheet structure, one portion of said sheet structure forming an elongated downwardly concave trough bearing external means for supporting an elongated light source, the remaining portion of said sheet structure being provided with perforations for rendering said remaining portion substantially acoustically transparent, a blanket of fibrous sound-absorbing material secured to the inner side of said remaining portion, said sheet and said blanket being so shaped as to form an empty space on the interior thereof, and means for hanging said sheet structure from a ceiling.

3. A combined lighting and sound-absorbing fixture comprising: a tubular sheet structure, one portion of said sheet structure forming an elongated downwardly concave trough bearing external means for supporting an elongated light source, the remaining portion of said sheet structure being provided with perforations for rendering said remaining portion substantially acoustically transparcut, a body of fibrous sound-absorbing material secured within said tubular member in sound absorption relationship with said perforations, said sheet and said blanket being so shaped as to form an empty space on the interior thereof, and means attached to the inner side of said trough portion and extending through the opposite Wall of said tubular sheet structure for hanging said sheet structure from a ceiling.

4. A combined lighting and sound absorbing fixture comprising: a tubular sheet structure having a cross-section of substantially oval configuration except for a reentrant portion forming an elongated trough bearing external means for supporting an elongated light source, the oval portion of said sheet structure being provided with perforations for rendering said oval portion substanitally acoustically transparent, a blanket of fibrous sound absorbing material secured to the inner side of said oval portion and enclosing a cavity, and means for hanging said sheet structure from a ceiling.

5. A fixture as defined in claim 4 wherein the major and minor axes of said oval cross-section extend horizontally and vertically respectively.

6. A combined lighting and sound-absorbing fixture comprising: a tubular sheet structure of cylindrical configuration having a reentrant portion forming an elongated trough bearing external means for supporting an elongated light source, the non-reentrant portion of said sheet structure being provided with perforations for rendering said non-reentrant portion substantially acoustically transparent, a blanket of fibrous sound-absorbing material secured to the inner side of said non-reentrant portion, and means for hanging said sheet structure from a ceiling.

7. A combined lighting and sound-absorbing fixture for use in a room comprising: holding means including a downwardly concave trough for supporting a light below a ceiling in room-illuminating position, a pair of cylindrical sheet members secured to opposite edges of said trough and extending upwardly toward said ceiling, said cylindrical sheets being provided with perforations for rendering them acoustically transparent, a blanket of fibrous sound-absorbing material secured to the upper side of each of said cylindrical sheets, and means connected to the upper edges of said sheets for supporting the same from the ceiling.

8. A combined lighting and sound absorbing fixture for use in a room comprising: means including a downwardly concave trough having lower edges thereof extending substantially laterally, said trough being adapted to support a light spaced below a ceiling in room-illuminating position, a body of fibrous sound-absorbing material contiguous with said trough adjacent said edges and substantially laterally extending from said edges and completely surrounding the side and top portions of said trough, said body being spaced above the top portion of said trough thereby to define a substantially enclosed air space between said body and said trough, said material being adapted to absorb sound waves, said material being exposed to the ambient air in said room for absorbing a large proportion of all sound waves impinging thereon, and a common structure for suspending said trough and said material from such ceiling in position to receive and absorb both direct and reflected sound waves, including the sound waves reflected from said ceiling.

9. A combined lighting and sound absorbing fixture suspended from a ceiling of a room, said fixture comprising: an elongated downwardly concave trough, members in said trough for supporting an elongated light source within the concave side thereof, a body of fibrous soundabsorbing material having edges thereof attached to lower edges of said trough on the opposite side thereof from such light and completely surrounding the convex side of said trough, said material being spaced from said convex side of said trough to define an air space between said material and the convex side of said trough, said material being exposed to the ambient air in said room and being adapted to absorb a large proportion of sound waves impinging thereon, said material being arranged to absorb direct and reflected sound waves including the sound waves reflected from said ceiling, whereby a larger proportion of the sound waves is absorbed than would be absorbed by a perfectly absorptive horizontally disposed plate having the same shape and dimensions as a horizontal plane extending through said fixture, and common means attached directly to said trough for suspending said trough and said body of material below the ceiling of said room.

10. The combination of claim 9 including a thin rigid elongated sheet conforming to the configuration of said sound-absorbing material and covering said body of sound-absorbing material, said sheet being provided with perforations for rendering it substantially acoustically transparent to sound Waves.

References Cited in the file of this patent UNITED STATES PATENTS 1,760,500 Norris Aug. 27, 1929 1,992,509 Slidell Feb. 26, 1935 2,011,252 Modigliani Aug. 13, 1935 2,123,358 Grutzner July 12, 1938 2,160,638 Bedell May 30, 1939 2,281,379 Ohm Apr. 28, 1942 2,306,597 Darley Dec. 29, 1942 2,306,685 Chambers c- Dec. 29, 1942 2,334,484 Dunbar Nov. 16, 1943 2,335,218 Vacha Nov. 23, 1943 2,348,930 Schepmoes Mayv 16, 1944 2,390,262 Mazer Dec. 4, 1945 2,502,016 Olson Mar. 28, 1950 2,502,017 Beers Mar. 28, 1950 2,506,634 Wince May 13, 1952 2,610,695 Grue Sept. 16, 1952 2,659,807 Wakefield Nov. 17, 1953 FOREIGN PATENTS 114,518 Australia Jan. 22, 1942 629,351 Great Britain Sept. 19, 1949 593,235 Great Britain Oct. 10, 1947 

